Your GF needs more information.
Albeit the options vest over a four year period, there can be a constraint where the shares cannot be sold, or cannot be sold until the company is sold and only then are they cashed out, and on and on,...because share value is established in the sale and not before.
Or,...if GF leaves after 3 years are the vested options retained for her individual account or will she forfeit? The caveat can be, she is "vested" with options under her control as long as she is an employee.
Do the vested options go away if she goes to work for a competitor? Who and What defines "competitor"?
There has to be a company legal document in place that defines the options process. If the company will not share that document, consider the options as a "zero" benefit and look for other benefits that would entice her to work for this specific company.
....been here, done this....I went to work for a similar scenario company because I liked the company and the job....the shares meant zero to me, but I was older. If the opportunity happened to me when I was younger, I wouldn't have gone to work for that company. The sales pitch to one of these option/share deals can sound exciting, the reality is very few employees collect.
